1. Field of the Invention
The present invention relates to a speech system which prevents a third party from eavesdropping on the contents of a conversational speech and a speech processing method and apparatus and a storage medium which are used for the system.
2. Description of the Related Art
When people have a conversation in an open space or a non-soundproof room, the leakage of conversation may be a problem. Assume that a customer has a conversation with a bank clerk or an outpatient has a conversation with a receptionist or doctor in a hospital. In this case, if a third party overhears the conversation, it may violate secrecy or privacy.
Under the circumstances, there have been proposed techniques of preventing a third party from eavesdropping on a conversation by using a masking effect (see, for example, Tetsuro Saeki, Takeo Fujii, Shizuma Yamaguchi, and Kensei Oimatsu, “Selection of Meaningless Steady Noise for Masking of Speech”, the transactions of the Institute of Electronics, Information and Communication Engineers, J86-A, 2, 187-191, 2003 and Jpn. Pat. Appln. KOKAI Publication No. 5-22391). The masking effect is a phenomenon in which when a person hearing a given sound hears another sound at a predetermined level or more, the original sound is canceled out, and the person cannot hear it. There is available, as a technique of preventing a third party from hearing an original sound by using such the masking effect, a method of superimposing pink noise or background music (BGM) as a masking sound on an original sound. As proposed by Tetsuro Saeki, Takeo Fujii, Shizuma Yamaguchi, and Kensei Oimatsu, “Selection of Meaningless Steady Noise for Masking of Speech”, the transactions of the Institute of Electronics, Information and Communication Engineers, J86-A, 2, 187-191, 2003 band-limited pink noise is, in particular, regarded as most effective.